An increasing number of recent electronic apparatus, more specifically portable terminal units of a portable telephone system among other equipment, illuminate their push buttons, display sheets, etc. using light emitting diodes, electro luminescent elements or the like devices in order to facilitate easier operation of the units and clearer recognition of messages. The illuminating means are requested to be able to provide lights for creating various modes at inexpensive cost.
A conventional movable contact element and a switch incorporating the contact element are described in the following with reference to FIG. 7. FIG. 7 shows a cross sectional view of a conventional switch. In FIG. 7, transparent light conducting sheet 1 in a flexible film state is formed of light conducting layer 1A sandwiched by upper protective layer 1B and lower protective layer 1C. For easier description of the film structure, the drawings are shown enlarged in the direction of film thickness. A plurality of movable contact points 3 made of a thin conductive metal sheet in an approximate dome shape are affixed to the lower surface of light conducting sheet 1 using an adhesive agent (not shown), and light conducting layer 1A has at the location above movable contact point 3 a plurality of light causing sections 1D which are of an uneven shape. Movable contact element 4 has such a make-up.
On the upper surface of substrate 5 having a plurality of circuit patterns (not shown) formed at the upper and lower surfaces, a plurality of fixed contact points 6 are provided, which fixed contact points including central fixed contact point 6A of approximate round shape and a plurality of outer fixed contact points 6B of a horse shoe shape surrounding the central fixed contact point. Movable contact point 3 is disposed above the fixed contact points in a manner where the outer circumference is resting on outer fixed contact points 6B while the center of lower surface is opposing to central fixed contact point 6A with a certain specific clearance secured in between. A plurality of light emitting diodes or the like light emitting devices 7 are mounted on substrate 5 at a place which is the right to light conducting sheet 1. The light emitting face of light emitting device 7 opposes to the end-face of light conducting layer 1A of light conducting sheet 1 at the right. Operating body 8 made of an insulating resin material in a sheet form includes transparent portion 8A and light blocking portion 8B covering the above. Each of a plurality of operating sections 8C has at the top plane its specific display section 8D, where transparent portion 8A is exposed to demonstrate a certain specific letter or a symbol of its own. Pressing section 8E, which is protruding downward, is having contact with the upper surface of light conducting sheet 1 at the location corresponding to the center of movable contact point 3. A conventional switch is structured as such.
A switch having the above-described make-up is mounted on the operation panel of an electronic apparatus, and central fixed contact point 6A, outer fixed contact points 6B and light emitting device 7 are connected via circuit pattern with an electronic circuit (not shown) of the electronic apparatus.
When a certain specific operating section 8C of operating body 8 is pressed downward, pressing section 8E corresponding to the operating section gives pressure on the upper surface of light conducting sheet 1. Light conducting sheet 1 bends to press down movable contact point 3 of an approximate dome shape at the center. As soon as the pressing force reaches at a certain level, movable contact point 3 elastically reverses accompanying a click feeling, to make contact at the center of the lower surface with central fixed contact point 6A. Then, central fixed contact point 6A and outer fixed contact point 6B are electrically connected via movable contact point 3. When the pressing force given on operating section 8C is withdrawn, movable contact point 3 reverses back upward due to elastic self restorative force, and the center of lower surface departs from central fixed contact point 6A, leaving the electrical connection between central fixed contact point 6A and outer fixed contact point 6B disconnected. The operation of an electronic apparatus is switched to perform different functions in accordance with the above-described procedure of electrical connection/disconnection.
If, at this moment, a certain voltage is applied on light emitting device 7 from the electronic circuit of electronic apparatus, light emitting device 7 starts generating light, which light goes into light conducting layer 1A from the right end-face of light conducting sheet 1 to illuminate the entire light conducting layer 1A. The light is reflected by light causing section 1D of the uneven shape within light conducting layer 1A; thus, a plurality of light causing sections 1D generates light. The light proceeds through upper protective layer 1B to illuminate display section 8D of operating body 8 from the underneath. In this way, an operator can easily recognize the letters or symbols of respective operating sections 8C even in a dark environment.
Patent Document 1 is an example of prior art technical information related to the present patent application.
In the above-described conventional movable contact element and a switch incorporating the movable contact element, a plurality of light emitting devices 7 provides light for the entire portion of light conducting layer 1A of light conducting sheet 1. A plurality of display sections 8D of operating body 8 is illuminated with the light; viz. the color of light emitted from light emitting device 7 determines the illumination color for operating body 8. This means that a plurality of light causing sections 1D can generate only a single color. Furthermore, each time when other illuminating color is needed, other light emitting device 7 had to be used or different light emitting devices had to be used in combination. This takes extra time. This was a problem for making illumination with different colors in various modes.
Patent Document 1                Japanese Patent Unexamined Publication No. 2006-318905        